The VideoLAN Forums

Posted: **06 May 2014 15:15**

Hi I am trying to track down an issue in latest VLC nightly live streaming HLS. The command I'm using to start the stream looks like this:

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vlc.exe -I rc -vvv dshow:// :dshow-vdev="Osprey-230 Video Device 1" :dshow-size=640x480 :dshow-aspect-ratio="4\:3" :dshow-fps=29.97 :dshow-video-input=0 :dshow-video-output=0  :dshow-adev="Balanced 1 (Osprey-2X0)" :dshow-audio-channels=2 :dshow-audio-samplerate=44100 :dshow-audio-bitspersample=16  --sout=#duplicate{dst={transcode{width=640,height=480,fps=29.97,vcodec=h264,vb=1000,venc=x264{preset=superfast,keyint=90,ref=1},acodec=mp3,ab=96,channels=2,samplerate=44100}:std{access=livehttp{startseg=500,seglen=10,delsegs=true,numsegs=5,index=D:\live\WIFI-1096k-360p\WIFI-1096k-360p.m3u8,index-url=http://10.0.2.105/live/WIFI-1096k-360p/WIFI-1096k-360p-########.ts},mux=ts{use-key-frames},dst=D:\live\WIFI-1096k-360p\WIFI-1096k-360p-########.ts}}}

This will crash vlc almost immediately. Using a debug build I managed to get a backtrace using gdb:

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Program received signal SIGSEGV, Segmentation fault.
0x6f22a8fb in libebml::EbmlId::EbmlId (
    this=0x75dff544 <msvcrt!.dllonexit+59>, aValue=1865190780, aLength=191)
    at ../../../libebml/ebml/EbmlId.h:69
69      ../../../libebml/ebml/EbmlId.h: No such file or directory.
(gdb) bt
#0  0x6f22a8fb in libebml::EbmlId::EbmlId (
    this=0x75dff544 <msvcrt!.dllonexit+59>, aValue=1865190780, aLength=191)
    at ../../../libebml/ebml/EbmlId.h:69
#1  0x6f1fcb6b in __static_initialization_and_destruction_0 (
    __initialize_p=1, __priority=65535) at ../../src/EbmlCrc32.cpp:53
#2  0x6f1fcbb3 in _GLOBAL__sub_I__ZN7libebml9EbmlCrc3210ClassInfosE ()
    at ../../src/EbmlCrc32.cpp:353
#3  0x6f209daa in __do_global_ctors ()
    at ../../mingw-w64/mingw-w64-crt/crt/gccmain.c:44
#4  0x6f1b1305 in __DllMainCRTStartup (
    hDllHandle=hDllHandle@entry=0x6f1b0000, dwReason=1,
    lpreserved=lpreserved@entry=0x0)
    at ../../mingw-w64/mingw-w64-crt/crt/crtdll.c:200
#5  0x6f1b1443 in DllMainCRTStartup@12 (hDllHandle=0x6f1b0000, dwReason=1,
    lpreserved=0x0) at ../../mingw-w64/mingw-w64-crt/crt/crtdll.c:171
#6  0x772699a0 in ntdll!RtlQueryEnvironmentVariable ()
   from C:\Windows\system32\ntdll.dll
#7  0x6f1b0000 in ?? ()
#8  0x7726d939 in ntdll!LdrResSearchResource ()
   from C:\Windows\system32\ntdll.dll
#9  0x6f1b1420 in __DllMainCRTStartup ()
    at ../../mingw-w64/mingw-w64-crt/crt/crtdll.c:201
#10 0x7726d7fc in ntdll!LdrResSearchResource ()
   from C:\Windows\system32\ntdll.dll
---Type <return> to continue, or q <return> to quit---
#11 0x00000000 in ?? ()
(gdb)

After some googling I found that the ebml library where the crash is is used by the mkv demuxer, so I removed that dll fromt he plugins folder. Now it crashes in the x264 library. Stacktrace below:

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Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1516.0xec0]
0x75e079c8 in msvcrt!memcmp () from C:\Windows\syswow64\msvcrt.dll
(gdb) bt
#0  0x75e079c8 in msvcrt!memcmp () from C:\Windows\syswow64\msvcrt.dll
#1  0x6a32965c in x264_cqm_init (h=h@entry=0x283cff0) at common/set.c:95
#2  0x6a2a3d66 in x264_encoder_open_128 (param=param@entry=0x6bafec)
    at encoder/encoder.c:1154
#3  0x6a292cfc in Open (p_this=0x6c8d14)
    at ../../extras/package/win32/../../../modules/codec/x264.c:1401
#4  0x718de5e0 in module_load (obj=obj@entry=0x6c8d14, m=m@entry=0x615268,
    init=init@entry=0x718de590 <generic_start>,
    args=args@entry=0x8dcfd44 "\024\215l")
    at ../../extras/package/win32/../../../src/modules/modules.c:185
#5  0x718de8fd in vlc_module_load (obj=obj@entry=0x6c8d14,
    capability=capability@entry=0x72b0b55a <pi_channels_maps+346> "encoder",
    name=0x693df4 "", name@entry=0x693df0 "x264", strict=strict@entry=true,
    probe=probe@entry=0x718de590 <generic_start>)
    at ../../extras/package/win32/../../../src/modules/modules.c:277
#6  0x718df004 in module_need (obj=obj@entry=0x6c8d14,
    cap=cap@entry=0x72b0b55a <pi_channels_maps+346> "encoder",
    name=name@entry=0x693df0 "x264", strict=strict@entry=true)
    at ../../extras/package/win32/../../../src/modules/modules.c:366
#7  0x72b051f2 in transcode_video_new (p_stream=p_stream@entry=0x6977cc,
    id=id@entry=0x6af500)
    at ../../../extras/package/win32/../../../modules/stream_out/transcode/video
.c:240
#8  0x72b06185 in transcode_video_add (p_stream=p_stream@entry=0x6977cc,
---Type <return> to continue, or q <return> to quit---

Some more googling I found this same exception was introduced because of some optimizations in gcc 4.8: http://forum.doom9.org/showthread.php?p=1623567 the solution offered was compiling using the extra cflag: --extra-cflags=-fno-aggressive-loop-optimizations, but in the same post in mentions that this has been fixed in x264: http://git.videolan.org/?p=x264.git;a=c ... 3eb8eeef44 Since VLC uses HEAD for x264 I would think this wouldn't be an issue any longer.

Back in november I developed a patch for the livehttp module: http://git.videolan.org/?p=vlc.git;a=co ... 850987e240 and I know when I developed that patch things were working. Does anyone know of anything that has changed since that might introduce these crashes? Something with the build scripts maybe, or updates to gcc / mingw? I wish I was able to track this down further, but I'm not very experienced C developer, especially with a codebase as large as VLC. If anyone could point me int he right direction, I'm willing to do any grunt work to get this working again.

Thanks

-ray

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2.2 Crashes Live Streaming HLS

2.2 Crashes Live Streaming HLS